Now that I've finally been able to access the air filter on my 08 3 I was thinking of drilling two or three 3/4 inch holes in the lid of the air box where there are obstructions in order to get more air flow thru all the plastic that surely must inhibit air flow. Has anyone done this mod and if so what, if any, improvement did it make?
Thanks for any replies.

 

A waste of time and energy; drilling the airbox will do absolutely nothing good for performance. That said, such an action may well allow warmer engine bay air to enter the intake, and while that may aid fuel atomization a tiny bit (which may in turn ever-so-slightly aid fuel economy on a very cold day), the affect on engine performance may well be negative.

 

While theories are always interesting, I was hoping to get actual practical replies from someone who had actually done this procedure. However, thanks for your input. Until recently I was a long time XC dirt bike & sport quad rider and one of the first improvements I would make on a new machine would be to drill the air box and add an after market exhaust system, whis always made a significant performance improvement thruout the power band.Never was there a down side to this mod unless one had an objection to a slightly louder exhaust note
Never the less, in the absence of any other replies, I have deferred to your theory and just finished installing a new filter without any modification.

 

another note from a 'didn't make that mod' person...
The intake, lengths / volumes etc... are designed to give a particular performance curve to the engine. Different amounts of airmass (tube length) effect the torque since there's a different amount of air trying to enter the engine as a column... intake pulses and the air column tries to be a train moving at a constant speed.
Its possible you'll make an improvement, but you can always tape the hole back shut if you see it make things worse.

To the point of shipo, adding warm air isn't what you want to do, so adding some piping to the front of the radiator support would be recommended.

I did add a hole near the bottom of the intake, right near the horn, and on the front side to give a little ram air effect as that's where the air is pressurised a bit from vents in the front bumper. I saw about 1mpg improvement in highway mileage - though that's still pretty close to noise.

Good luck, let us know what sort of change there is in performance.